<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
<style>
    body{
        text-align:center;
    }
    /* 如何内联元素或内联块元素水平居中
    1、改变元素自身的display属性，使用margin-left,margin-right方案
    2、给它爹设置text-align:center; */
</style>
</head>
<body>
    <div>
    <a href="dd">ddddd</a><br>
    <button>btn</button>
    </div>  
</body>
</html>